SPEC’ing Out A Clutch for our Supercharged E46 M3

Your clutch is one of the few driveline components you can feel and it can become a very personal choice. The exertion required to move the pedal, along with the engagement point and feel are all easily perceived. For most enthusiasts, we want the softest, smoothest engaging clutch that is able to hold whatever power level you’re making. Though, as power increases, typically so does the harshness of engagement. While the engine for our Project M-Track3r was out, we felt like it would be a good time to install a new clutch. We turned to SPEC Clutch andx the Stage 2+ clutch kit (PN SB663FHS) and steel flywheel (PN SB64S).

The SPEC Stage 2+ clutch kit comes complete with a billet pressure plate, disc, release bearing, pilot bearing, and clutch disc alignment tool. For an additional cost, we added the steel flywheel option which also comes with new flywheel fasteners.

Project M-Track3r makes 400 rwhp through its ESS/Vortech supercharged stock engine. Being something that’s going to spend a lot of time on the street and the road course, the clutch needed to stand up to the rigors of both environments. Since we are not creating a ton of power, we didn’t feel like a twin-disc clutch was needed and a single setup would suffice. With our engine back together, we enlisted the help of Formula Drift champion Michael Essa at Essa Autosport to help us install the clutch kit onto our completed E46 S54 long-block.

SPEC clearly labels the direction of each clutch disc via a sticker on the hub, making it virtually impossible to install the disc backwards.

“The Stage 2+ with enhanced hybrid is very popular with those who want the smoothest possible engagement in a high torque application,” explained David Norton of SPEC Clutch. “With a capacity just shy of 540 lb-ft, the hybrid fiber and carbon graphite full-faced disc provides a smooth, manageable engagement from a stop and a more progressive high speed engagement, making it driveline-friendly.”

Billet pressure plates come standard on E46 clutches to keep the rotating assembly as light as possible. SPEC touts that it provides the highest level of safety versus cast iron while producing a friendly pedal requirement. This clutch kit is good for any combination of street and competition environments.

Our E46’s S54 engine spun a rod bearing while tire testing at Willow Springs. Now the engine is back together and it’s time to get the engine mated to the transmission. Before we do that, we need to install our SPEC clutch.

We have seen a 10-whp gain from the S54 flywheel – David Norton, SPEC Clutch

When it comes to flywheels, there’s two options. “Our 10-pound aluminum flywheel is half the weight of our steel single mass flywheel and 15-pounds lighter than the original dual mass flywheel, thus, creating a 60 percent reduction in mass,” explained Norton. “Given equal diameter, the MOI (moment of inertia) is reduced by 60 percent. The mass reduction not only raises horsepower across the rev range and increases rate of revving, it is also easier on the engine and more responsive to throttle changes. We have seen a 10-whp gain from the S54 flywheel.” We opted to stick with the steel flywheel, though, to keep the same inertia at RPM so the driving characteristics would remain the same.

Installation

Installing SPEC’s flywheel and clutch is as simple as an OEM replacement. They include new bolts, pilot bearing and slave cylinder. We really like SPEC’s billet bearing housing for the clutch release bearing.

With the pilot bearing installed into the back of the clutch, the flywheel easily slips onto the back of the crank. A little red or blue thread sealant helps ensure these bolts won’t back out.

The flywheel is doweled so it only goes on one way. To keep the engine from spinning, a bolt and a pry bar on the starter engagement ring (plus the help from a friend) makes life a lot easier. Torque to 77 ft-lbs in a star pattern much like lug nuts.

Remember that flywheel side sticker? Yep, make sure it faces the flywheel and install the clutch plate alignment tool.

Each SPEC clutch and flywheel are balanced together. A paint mark from the pressure plate to the flywheel helps keep from mis-aligning the assembly and causing a driveline vibration.

A new set of cap screws hold the flywheel on the clutch. Again, more thread sealant and torque in a star pattern to 18 ft-lbs.

The SPEC clutch release bearing installs directly in place of the factory bearing. Installing a new pilot and clutch release bearing at the time of a clutch install is always recommended. The worst sound is that release bearing screech right after getting everything back together!

At that is that! Our SPEC clutch is installed and our transmission is ready to go. From this point we will mate the engine and transmission together and get the combination back into the car. Before you know it we will have Project M-Track3r back on the road!